The piezoelectric effect, as it is called, has been known since 1880 and was discovered by J. and P. Curie. Such materials develop an electric charge in deformation under mechanical stress or they change their shape when an electric field is applied. The latter is also known as the “inverse piezoelectric effect” and is utilized in a variety of ways, especially in technology.
Some naturally occurring piezoelectric crystals such as quartz as well as a wide variety of synthetically produced ceramic materials such as titanates or niobates have good piezoelectric properties. Plastics having piezoelectric properties are also conventional. For example, the piezoelectric effect of the synthetic polymer polyvinylidene fluoride (PVDF) exceeds that of crystalline quartz by a factor of three to five.
So far, the change in shape of samples has been measured in the development of piezoactive materials. However, one disadvantage here is that minimal changes in shape are measured, especially when using comparatively small samples. This leads to comparatively slow, complicated and uneconomical methods of testing such materials, so that corresponding devices and methods can be used only to a limited extent, e.g., in the case of numerous material samples.